This document is available to the public through the National Technical Information Service, Spri... more This document is available to the public through the National Technical Information Service, Springfield, VA 22161This document is disseminated under the sponsorship of the Department of Transportation in the interest of information exchange. The United The Weather Systems Processor (WSP) modification to existing Airport Surveillance Radars (ASR-9) significantly enhances the functionality of the radar with respect to hazardous weather detection and tracking. Dedicated alphanumeric and color graphic displays alert controllers to hazardous wind shear conditions on the runways or final approach/initial departure flight corridors, show current location and anticipated movement of thunderstorm cells, and provide short-term forecasts of operationally significant wind shifts. Operational tests of a prototype WSP and related terminal area hazardous weather detection systems (the Terminal Doppler Weather Radar (TDWR) and the Integrated Terminal Weather System (ITWS » have shown that, in addi...
The objective of this study was to analyze the weather sensing and data fusion required to improv... more The objective of this study was to analyze the weather sensing and data fusion required to improve safety and reduce delays at a number of west coast airports that are not currently scheduled to receive Integrated Terminal Weather Systems (ITWS). This report considers the Los Angeles (LAX), San Francisco (SFO), Seattle (SEA) and Portland, OR (PDX) international airports. A number of visits were made to the various ATC facilities to better understand their weather decision support operational needs.
This analysis investigates which weather variables are correlated with arriving pilots' conve... more This analysis investigates which weather variables are correlated with arriving pilots' convective cell penetration/deviation behavior in the DFW terminal airspace. The report indicates that it is possible to train a statistical classifier that characterizes the probability that pilots will penetrate or deviate around airspace occupied by thunderstorms. The analysis outlines several desirable characteristics of a probability-of-deviation classifier. The classifiers trained and tested in this study were able to correctly classify more than 80% of the storm cell encounters in an independent data set. The analysis does not find any correlation between the weather variables and the pilot's penetration/deviation behavior near the destination airports. The vast majority of encounters near the airport in this study results in penetrations.
Journal of the National Cancer Institute. Monographs, 2010
We review design and analytic methods available for multilevel interventions in cancer research w... more We review design and analytic methods available for multilevel interventions in cancer research with particular attention to study design, sample size requirements, and potential to provide statistical evidence for causal inference. The most appropriate methods will depend on the stage of development of the research and whether randomization is possible. Early on, fractional factorial designs may be used to screen intervention components, particularly when randomization of individuals is possible. Quasi-experimental designs, including time-series and multiple baseline designs, can be useful once the intervention is designed because they require few sites and can provide the preliminary evidence to plan efficacy studies. In efficacy and effectiveness studies, group-randomized trials are preferred when randomization is possible and regression discontinuity designs are preferred otherwise if assignment based on a quantitative score is possible. Quasi-experimental designs may be used, e...
Journal of the National Cancer Institute. Monographs, 2010
Screening has become one of our best tools for early detection and prevention of cancer. The grou... more Screening has become one of our best tools for early detection and prevention of cancer. The group-randomized trial is the most rigorous experimental design for evaluating multilevel interventions. However, identifying the proper sample size for a group-randomized trial requires reliable estimates of intraclass correlation (ICC) for screening outcomes, which are not available to researchers. We present crude and adjusted ICC estimates for cancer screening outcomes for various levels of aggregation (physician, clinic, and county) and provide an example of how these ICC estimates may be used in the design of a future trial. Investigators working in the area of cancer screening were contacted and asked to provide crude and adjusted ICC estimates using the analysis of variance method estimator. Of the 29 investigators identified, estimates were obtained from 10 investigators who had relevant data. ICC estimates were calculated from 13 different studies, with more than half of the studie...
Researchers around the world are using Lot Quality Assurance Sampling (LQAS) techniques to assess... more Researchers around the world are using Lot Quality Assurance Sampling (LQAS) techniques to assess public health parameters and evaluate program outcomes. In this paper, we report that there are actually two methods being called LQAS in the world today, and that one of them is badly flawed. This paper reviews fundamental LQAS design principles, and compares and contrasts the two LQAS methods. We raise four concerns with the simply-written, freely-downloadable training materials associated with the second method. The first method is founded on sound statistical principles and is carefully designed to protect the vulnerable populations that it studies. The language used in the training materials for the second method is simple, but not at all clear, so the second method sounds very much like the first. On close inspection, however, the second method is found to promote study designs that are biased in favor of finding programmatic or intervention success, and therefore biased against the interests of the population being studied. We outline several recommendations, and issue a call for a new high standard of clarity and face validity for those who design, conduct, and report LQAS studies.
This document is available to the public through the National Technical Information Service, Spri... more This document is available to the public through the National Technical Information Service, Springfield, VA 22161This document is disseminated under the sponsorship of the Department of Transportation in the interest of information exchange. The United The Weather Systems Processor (WSP) modification to existing Airport Surveillance Radars (ASR-9) significantly enhances the functionality of the radar with respect to hazardous weather detection and tracking. Dedicated alphanumeric and color graphic displays alert controllers to hazardous wind shear conditions on the runways or final approach/initial departure flight corridors, show current location and anticipated movement of thunderstorm cells, and provide short-term forecasts of operationally significant wind shifts. Operational tests of a prototype WSP and related terminal area hazardous weather detection systems (the Terminal Doppler Weather Radar (TDWR) and the Integrated Terminal Weather System (ITWS » have shown that, in addi...
The objective of this study was to analyze the weather sensing and data fusion required to improv... more The objective of this study was to analyze the weather sensing and data fusion required to improve safety and reduce delays at a number of west coast airports that are not currently scheduled to receive Integrated Terminal Weather Systems (ITWS). This report considers the Los Angeles (LAX), San Francisco (SFO), Seattle (SEA) and Portland, OR (PDX) international airports. A number of visits were made to the various ATC facilities to better understand their weather decision support operational needs.
This analysis investigates which weather variables are correlated with arriving pilots' conve... more This analysis investigates which weather variables are correlated with arriving pilots' convective cell penetration/deviation behavior in the DFW terminal airspace. The report indicates that it is possible to train a statistical classifier that characterizes the probability that pilots will penetrate or deviate around airspace occupied by thunderstorms. The analysis outlines several desirable characteristics of a probability-of-deviation classifier. The classifiers trained and tested in this study were able to correctly classify more than 80% of the storm cell encounters in an independent data set. The analysis does not find any correlation between the weather variables and the pilot's penetration/deviation behavior near the destination airports. The vast majority of encounters near the airport in this study results in penetrations.
Journal of the National Cancer Institute. Monographs, 2010
We review design and analytic methods available for multilevel interventions in cancer research w... more We review design and analytic methods available for multilevel interventions in cancer research with particular attention to study design, sample size requirements, and potential to provide statistical evidence for causal inference. The most appropriate methods will depend on the stage of development of the research and whether randomization is possible. Early on, fractional factorial designs may be used to screen intervention components, particularly when randomization of individuals is possible. Quasi-experimental designs, including time-series and multiple baseline designs, can be useful once the intervention is designed because they require few sites and can provide the preliminary evidence to plan efficacy studies. In efficacy and effectiveness studies, group-randomized trials are preferred when randomization is possible and regression discontinuity designs are preferred otherwise if assignment based on a quantitative score is possible. Quasi-experimental designs may be used, e...
Journal of the National Cancer Institute. Monographs, 2010
Screening has become one of our best tools for early detection and prevention of cancer. The grou... more Screening has become one of our best tools for early detection and prevention of cancer. The group-randomized trial is the most rigorous experimental design for evaluating multilevel interventions. However, identifying the proper sample size for a group-randomized trial requires reliable estimates of intraclass correlation (ICC) for screening outcomes, which are not available to researchers. We present crude and adjusted ICC estimates for cancer screening outcomes for various levels of aggregation (physician, clinic, and county) and provide an example of how these ICC estimates may be used in the design of a future trial. Investigators working in the area of cancer screening were contacted and asked to provide crude and adjusted ICC estimates using the analysis of variance method estimator. Of the 29 investigators identified, estimates were obtained from 10 investigators who had relevant data. ICC estimates were calculated from 13 different studies, with more than half of the studie...
Researchers around the world are using Lot Quality Assurance Sampling (LQAS) techniques to assess... more Researchers around the world are using Lot Quality Assurance Sampling (LQAS) techniques to assess public health parameters and evaluate program outcomes. In this paper, we report that there are actually two methods being called LQAS in the world today, and that one of them is badly flawed. This paper reviews fundamental LQAS design principles, and compares and contrasts the two LQAS methods. We raise four concerns with the simply-written, freely-downloadable training materials associated with the second method. The first method is founded on sound statistical principles and is carefully designed to protect the vulnerable populations that it studies. The language used in the training materials for the second method is simple, but not at all clear, so the second method sounds very much like the first. On close inspection, however, the second method is found to promote study designs that are biased in favor of finding programmatic or intervention success, and therefore biased against the interests of the population being studied. We outline several recommendations, and issue a call for a new high standard of clarity and face validity for those who design, conduct, and report LQAS studies.
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Papers by D. Rhoda